The invention relates to a video signal processing system, and in particular to a system for processing both video data and graphic data to provide a mixed output signal.
Video signal processing systems often include a filter unit that converts video pictures from a first format to a second format. For example, the first format may be coded in accordance with the digital studio standard of the International Telecommunications Union UIT-R (or of the Comite Consultatif International des Radiocommunications: CCIR) 601. An example of converting from a first format to a second format is the conversion from a PAL 16×9 picture format with 720 pixels per line (P/L) and 576 lines (L), into the National Television System Committee (NTSC) 16×9 picture format, with 480 pixels per line and 480 lines.
In addition, video signal processing systems often include a computing unit for mixing video and graphic pictures (e.g., layering and alpha-blending). The computing unit for mixing may weight different pictures by adjustable factors (i.e., alpha blending), so that transparent pictures can be displayed by combining and superposing the images (i.e., layering). For example, transparent buttons may be inserted while the original video picture continues to be visible in the background.
At this time, such systems exist only as individual components. A disadvantage of combining such systems is the amount of memory required to filter and mix video and graphic pictures.
Therefore, there is a need for a memory efficient video signal processing system capable of converting video signals from a first format to second format, and mixing several pictures.